Cytokine-directed cellular cross-talk imprints synovial pathotypes in rheumatoid arthritis.

INTRODUCTION: Structural reorganisation of the synovium with expansion of fibroblast-like synoviocytes (FLS) and influx of immune cells is a hallmark of rheumatoid arthritis (RA). Activated FLS are increasingly recognised as a critical component driving synovial tissue remodelling by interacting with immune cells resulting in distinct synovial pathotypes of RA. METHODS: Automated high-content fluorescence microscopy of co-cultured cytokine-activated FLS and autologous peripheral CD4+ T cells from patients with RA was established to quantify cell-cell interactions. Phenotypic profiling of cytokine-treated FLS and co-cultured T cells was done by flow cytometry and RNA-Seq, which were integrated with publicly available transcriptomic data from patients with different histological synovial pathotypes. Computational prediction and knock-down experiments were performed in FLS to identify adhesion molecules for cell-cell interaction. RESULTS: Cytokine stimulation, especially with TNF-α, led to enhanced FLS-T cell interaction resulting in cell-cell contact-dependent activation, proliferation and differentiation of T cells. Signatures of cytokine-activated FLS were significantly enriched in RA synovial tissues defined as lymphoid-rich or leucocyte-rich pathotypes, with the most prominent effects for TNF-α. FLS cytokine signatures correlated with the number of infiltrating CD4+ T cells in synovial tissue of patients with RA. Ligand-receptor pair interaction analysis identified ICAM1 on FLS as an important mediator in TNF-mediated FLS-T cell interaction. Both, ICAM1 and its receptors were overexpressed in TNF-treated FLS and co-cultured T cells. Knock-down of ICAM1 in FLS resulted in reduced TNF-mediated FLS-T cell interaction. CONCLUSION: Our study highlights the role of cytokine-activated FLS in orchestrating inflammation-associated synovial pathotypes providing novel insights into disease mechanisms of RA.

Response to SARS-CoV-2 vaccination in systemic autoimmune rheumatic disease depends on immunosuppressive regimen: a matched, prospective cohort study.

OBJECTIVE: To assess the humoral response to messenger RNA (mRNA) vaccine of patients with systemic autoimmune rheumatic disease (SARD) and the effect of immunosuppressive medication in a matched cohort study. METHODS: Patients with SARD were enrolled and matched 1:1 for sex and age with healthy control (HC) subjects. Differences in humoral response to two doses of an mRNA vaccine in terms of seroconversion rate (SCR) and SARS-CoV-2 antibody level between the two groups and the impact of treatment within patients with SARD were assessed. RESULTS: We enrolled 82 patients with SARD and 82 matched HC. SCR after the first dose was lower among the patient group than that of HC (65% compared with 100% in HC, p<0.0001) but levelled up after the second dose (94% vs 100%). After the second dose, SCR was lower for patients on combination disease-modifying antirheumatic drug (DMARD) therapy compared with all other groups (81% compared with 95% for monotherapy, p=0.01; 100% for both no DMARD therapy and HC, both p<0.0001). In addition, antibody levels after both doses were lower in patients compared with HC. We found that vaccination response was determined primarily by the number of DMARDs and/or glucocorticoids received, with patients receiving combination therapy (dual and triple therapy) showing the poorest response. CONCLUSIONS: Patients with SARD showed a good response after the second vaccination with an mRNA vaccine. However, the choice of immunosuppressive medication has a marked effect on both SCR and overall antibody level, and the number of different immunomodulatory therapies determines vaccination response.

TNFR2 is critical for TNF-induced rheumatoid arthritis fibroblast-like synoviocyte inflammation.

OBJECTIVES: TNF-induced activation of fibroblast-like synoviocytes (FLS) is a critical determinant for synovial inflammation and joint destruction in RA. The detrimental role of TNF-receptor 1 (TNFR1) has thoroughly been characterized. The contributions of TNFR2, however, are largely unknown. This study was performed to delineate the role of TNFR2 in human FLS activation. METHODS: TNFR2 expression in synovial tissue samples was determined by immunohistochemistry. Expression of TNFR2 was silenced using RNAi or CRISPR/Cas9 technologies. Global transcriptional changes were determined by RNA-seq. QPCR, ELISA and immunoblotting were used to validate RNA-seq results and to uncover pathways operating downstream of TNFR2 in FLS. RESULTS: TNFR2 expression was increased in RA when compared with OA synovial tissues. In particular, RA-FLS demonstrated higher levels of TNFR2 when compared with OA-FLS. TNFR2 expression in RA-FLS correlated with RA disease activity, synovial T- and B-cell infiltration. TNF and IL1ß were identified as inflammatory mediators that upregulate TNFR2 in RA-FLS. Silencing of TNFR2 in RA-FLS markedly diminished the TNF-induced expression of inflammatory cytokines and chemokines, including CXCR3-binding chemokines and the B-cell activating factor TNFSF13B. Immunobiochemical analyses revealed that TNFR2-mediated expression of inflammatory mediators critically depends on STAT1. CONCLUSION: Our results define a critical role for TNFR2 in FLS-driven inflammation and unfold its participation in the unresolved course of synovial inflammation in RA.

The immunobiology of mTOR in autoimmunity.

The mechanistic target of rapamycin (mTOR) is a master regulator of the inflammatory response in immune and non-immune cells. In immune cells mTOR regulates metabolism to fuel cell fate decision, proliferation and effector functions. In non-immune cells, such as fibroblast, it controls inflammation-associated proliferation and migration/invasion, shapes the expression of cytokines and chemokines and promotes extracellular matrix remodeling and fibrosis. Hence, mTOR plays a critical role in chronic inflammation, where a continuous feedback between stromal cells and infiltrating immune cells result in tissue remodeling and organ damage. Activation of mTOR has been implicated in a number of chronic inflammatory diseases, especially rheumatic diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), systemic sclerosis (SSc), sjögren syndrome (SS) and seronegative spondyloarthropathy (SpA). Here we review recent advances in our understanding of the mechanism of mTOR activation in inflammation, especially in rheumatic diseases. We further discuss recent findings regarding the beneficial and side effects of mTOR inhibition in rheumatic conditions.

Histone deacetylase 1 (HDAC1): A key player of T cell-mediated arthritis.

Rheumatoid Arthritis (RA) represents a chronic T cell-mediated inflammatory autoimmune disease. Studies have shown that epigenetic mechanisms contribute to the pathogenesis of RA. Histone deacetylases (HDACs) represent one important group of epigenetic regulators. However, the role of individual HDAC members for the pathogenesis of arthritis is still unknown. In this study we demonstrate that mice with a T cell-specific deletion of HDAC1 (HDAC1-cKO) are resistant to the development of Collagen-induced arthritis (CIA), whereas the antibody response to collagen type II was undisturbed, indicating an unaltered T cell-mediated B cell activation. The inflammatory cytokines IL-17 and IL-6 were significantly decreased in sera of HDAC1-cKO mice. IL-6 treated HDAC1-deficient CD4+ T cells showed an impaired upregulation of CCR6. Selective inhibition of class I HDACs with the HDAC inhibitor MS-275 under Th17-skewing conditions inhibited the upregulation of chemokine receptor 6 (CCR6) in mouse and human CD4+ T cells. Accordingly, analysis of human RNA-sequencing (RNA-seq) data and histological analysis of synovial tissue samples from human RA patients revealed the existence of CD4+CCR6+ cells with enhanced HDAC1 expression. Our data indicate a key role for HDAC1 for the pathogenesis of CIA and suggest that HDAC1 and other class I HDACs might be promising targets of selective HDAC inhibitors (HDACi) for the treatment of RA.

FOXO3 is involved in the tumor necrosis factor-driven inflammatory response in fibroblast-like synoviocytes.

Fibroblast-like synoviocytes (FLS) are major contributors to joint inflammation in rheumatoid arthritis (RA). Forkhead box O 3 (FOXO3) perturbations in immune cells are increasingly linked to RA pathogenesis. Here, we show that FOXO3 is distinctly inactivated/phosphorylated in the FLS of rheumatoid synovitis. In vitro, stimulation of FLS with tumor necrosis factor-alpha α (TNFα) induced a rapid and sustained inactivation of FOXO3. mRNA profiling revealed that the inactivation of FOXO3 is important for the sustained pro-inflammatory interferon response to TNFα (CXCL9, CXCL10, CXCL11, and TNFSF18). Mechanistically, our studies demonstrate that the inactivation of FOXO3 results from TNF-induced downregulation of phosphoinositide-3-kinase-interacting protein 1 (PIK3IP1). Thus, we identified FOXO3 and its modulator PIK3IP1 as a critical regulatory circuit for the inflammatory response of the resident mesenchymal cells to TNFα and contribute insight into how the synovial tissue brings about chronic inflammation that is driven by TNFα.

Non-classical monocytes as mediators of tissue destruction in arthritis.

OBJECTIVES: Bone destruction in rheumatoid arthritis is mediated by osteoclasts (OC), which are derived from precursor cells of the myeloid lineage. The role of the two monocyte subsets, classical monocytes (expressing CD115, Ly6C and CCR2) and non-classical monocytes (which are CD115 positive, but low in Ly6C and CCR2), in serving as precursors for OC in arthritis is still elusive. METHODS: We investigated CCR2-/- mice, which lack circulating classical monocytes, crossed into hTNFtg mice for the extent of joint damage. We analysed monocyte subsets in hTNFtg and K/BxN serum transfer arthritis by flow cytometry. We sorted monocyte subsets and analysed their potential to differentiate into OC and their transcriptional response in response to RANKL by RNA sequencing. With these data, we performed a gene ontology enrichment analysis and gene set enrichment analysis. RESULTS: We show that in hTNFtg arthritis local bone erosion and OC generation are even enhanced in the absence of CCR2. We further show the numbers of non-classical monocytes in blood are elevated and are significantly correlated with histological signs of joint destruction. Sorted non-classical monocytes display an increased capacity to differentiate into OCs. This is associated with an increased expression of signal transduction components of RANK, most importantly TRAF6, leading to an increased responsiveness to RANKL. CONCLUSION: Therefore, non-classical monocytes are pivotal cells in arthritis tissue damage and a possible target for therapeutically intervention for the prevention of inflammatory joint damage.

Targeted inhibition of Janus kinases abates interfon gamma-induced invasive behaviour of fibroblast-like synoviocytes.

Objectives: The aim was to explore the function of the T-cell cytokine IFNγ for mesenchymal tissue remodelling in RA and to determine whether IFNγ signalling controls the invasive potential of fibroblast-like synoviocytes (FLS). Methods: To assess architectural responses, FLS were cultured in three-dimensional micromasses. FLS motility was analysed in migration and invasion assays. Signalling events relevant to cellular motility were defined by western blots. Baricitinib and small interfering RNA pools were used to suppress Janus kinase (JAK) functions. Results: Histological analyses of micromasses revealed unique effects of IFNγ on FLS shape and tissue organization. This was consistent with accelerated migration upon IFNγ stimulation. Given that cell shape and cell motility are under the control of the focal adhesion kinase (FAK), we next analysed its activity. Indeed, IFNγ stimulation induced the phosphorylation of FAK-Y925, a phosphosite implicated in FAK-mediated cell migration. Small interfering RNA knockdown of JAK2, but not JAK1, substantially abrogated FAK activation by IFNγ. Correspondingly, IFNγ-induced FAK activation and invasion of FLS was abrogated by the JAK inhibitor, baricitinib. Conclusion: Our study contributes insight into the synovial response to IFNγ and reveals JAK2 as a potential therapeutic target for FLS-mediated joint destruction in arthritis, especially in RA.

The RNA-binding protein HuR/ELAVL1 regulates IFN-ß mRNA abundance and the type I IFN response.

Secretion of type I interferon (IFN) is the first cellular reaction to invading pathogens. Despite the protective function of these cytokines, an excessive response to their action can contribute to serious pathologies, such as autoimmune diseases. Transcripts of most cytokines contain adenylate-uridylate (A/U)-rich elements (AREs) that make them highly unstable. RNA-binding proteins (RBPs) are mediators of the regulatory mechanisms that determine the fate of mRNAs containing AREs. Here, we applied an affinity proteomic approach and identified lethal, abnormal vision, drosophila-like 1 (ELAVL1)/Hu antigen R (HuR) as the predominant RBP of the IFN-ß mRNA ARE. Reduced expression or chemical inhibition of HuR severely hampered the type I IFN response in various cell lines and fibroblast-like synoviocytes isolated from joints of rheumatoid arthritis patients. These results define a role for HuR as a potent modulator of the type I IFN response. Taken together, HuR could be used as therapeutic target for diseases where type I IFN production is exaggerated.

Abatacept (CTLA-4Ig) treatment reduces T cell apoptosis and regulatory T cell suppression in patients with rheumatoid arthritis.

OBJECTIVE: Abatacept (CTLA-4Ig) blocks CD28-mediated T cell activation by binding to the costimulatory B7 ligands CD80/CD86 on antigen presenting cells. Costimulatory molecules, however, can also be expressed on T cells upon activation. Therefore, the aim of our study was to investigate direct effects of CTLA-4Ig on distinct T cell subsets in RA patients. METHODS: Phenotypic and functional analyses of CD4(+) T cells, including CD4(+) FoxP3(+) CD25(+) regulatory T cells (Treg), from RA patients were performed before and during CTLA-4Ig therapy. In addition T cells from healthy volunteers were analysed on in vitro culture with CTLA-4Ig or anti-CD80 and anti-CD86 antibodies. Apoptotic DNA fragmentation in CD4(+) and CD4(+) FoxP3(+) T cells was measured by TUNEL staining. RESULTS: We observed an increase in T cells, including Treg cells, after initiation of CTLA-4Ig therapy, which was linked to a downregulation of activation-associated marker molecules and CD95 on CD4(+) T cells and Treg cells. CTLA-4Ig decreased CD95-mediated cell death in vitro in a dose-dependent manner. Functional analysis of isolated Treg cells from RA patients further revealed a diminished suppression of responder T cell proliferation. This was found to be due to CTLA-4Ig-mediated blocking of CD80 and CD86 on responder T cells that led to a diminished susceptibility for Treg cell suppression. CONCLUSION: CTLA-4Ig therapy in RA patients exerts effects beyond the suppression of T cell activation, which has to be taken into account as an additional mechanism of CTLA-4Ig treatment.

[Biologics in SLE]. / Biologika bei SLE.

Biologics have become indispensable in the last decade in the treatment of the more common rheumatic diseases. For treating systemic lupus erythematodes (SLE), B-cell depletion, albeit off-label, has been a well-accepted strategy in severe and refractory disease. Unexpectedly, however, the results of the first randomized controlled rituximab trials in SLE were negative. New trials with improved study protocols are ongoing, which should resolve this issue. In 2012, with the approval of belimumab, SLE finally entered the era of approved biological therapies. The anti-Blys/BAFF antibody belimumab showed prevention of SLE flares, glucocorticoid sparing, and significant improvement in the quality of life of SLE patients, in part by drastically reducing immune complex mediated fatigue. Positive reports on further targeting approaches give hope that additional biological agents will be available for SLE therapy soon.

Amino Acids Fueling Fibroblast-Like Synoviocyte Activation and Arthritis By Regulating Chemokine Expression and Leukocyte Migration.

OBJECTIVE: We analyzed the impact of amino acid (AA) availability on the inflammatory response in arthritis. METHODS: We stimulated rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLSs) with tumor necrosis factor (TNF) in the presence or absence of proteinogenic AAs and measured their response by QuantSeq 3' messenger RNA sequencing, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay. Signal transduction events were determined by Western blot. We performed K/BxN serum transfer arthritis in mice receiving a normal and a low-protein diet and analyzed arthritis clinically and histologically. RESULTS: Deprivation of AAs decreased the expression of a specific subset of genes, including the chemokines CXCL10, CCL2, and CCL5 in TNF-stimulated FLSs. Mechanistically, the presence of AAs was required for the TNF-induced activation of an interferon regulatory factor 1 (IRF1)-STAT1 signaling circuit that drives the expression of chemotactic factors. The expression of IRF1 and the IRF1-dependent gene set in FLSs was highly correlated with the presence of inflammatory cells in human RA, emphasizing the important role of this AA-dependent pathway in inflammatory cell recruitment to the synovial tissue. Finally, we show that mice receiving a low-protein diet expressed less IRF1 in the inflamed synovium and consequently developed reduced clinical and histologic signs of arthritis. CONCLUSION: AA deprivation reduces the severity of arthritis by suppressing the expression of IRF1-STAT1-driven chemokines, which are crucial for leukocyte recruitment to the arthritic joint. Overall, our study provides novel insights into critical determinants of inflammatory arthritis and may pave the way for dietary intervention trials in RA.

Interferon signals and monocytic sensitization of the interferon-γ signaling pathway in the peripheral blood of patients with rheumatoid arthritis.

OBJECTIVE: Both type I interferons (IFNα and IFNß) and type II IFN (IFNγ) signal via pSTAT-1. Immunohistochemistry and the gene expression signatures of rheumatoid arthritis (RA) synovial tissue suggest an activated IFN/STAT-1 signaling pathway. The aim of this study was to determine the systemic activity of the IFN/STAT-1 signaling pathway in the peripheral blood cells of patients with RA. METHODS: Fluorocytometry or quantitative polymerase chain reaction was used to measure the expression of STAT-1, pSTAT-1, and IFN-inducible genes (monokine induced by interferon-γ [MIG], interferon-γ-inducible protein 10 [IP-10], and 2',5'-oligoadenylate synthetase [OAS]) in the peripheral blood mononuclear cells (PBMCs) and purified CD14+ peripheral blood monocytes of patients with RA and healthy control subjects. PBMCs were also incubated for 48 hours with IFNs and several other cytokines to investigate influences on STAT-1 levels. To examine the significance of STAT-1 activation in RA monocytes after stimulation with IFNγ, the expression of pSTAT-1 and of the IFNγ-inducible chemokine MIG was measured using fluorocytometry. RESULTS: Levels of STAT-1 were significantly increased in peripheral lymphocytes and monocytes from patients with RA compared with those from healthy control subjects. STAT-1 levels correlated well with RA disease activity, as measured by the Disease Activity Score in 28 joints and the Clinical Disease Activity Index. Furthermore, STAT-1 messenger RNA expression in RA CD14+ monocytes correlated with the expression of other IFN-target genes, such as IP-10, OAS, or MIG. In RA PBMCs, STAT-1 expression was increased not only by IFNs but also by tumor necrosis factor. RA monocytes demonstrated a considerably higher increase in pSTAT-1 and MIG levels upon IFNγ stimulation when compared with monocytes from control subjects, indicating that RA monocytes are more sensitive to IFNγ stimulation. CONCLUSION: In addition to supporting the role of IFNs in systemic proinflammatory activity, the results of this study further suggest preactivation of the IFNγ/STAT-1 signaling pathway, especially in RA monocytes.

CCL17/thymus and activation-related chemokine in Churg-Strauss syndrome.

OBJECTIVE: Churg-Strauss syndrome (CSS) is a Th2-mediated systemic vasculitis characterized by eosinophilic infiltration, blood eosinophilia, and high IgE levels. CCL17/thymus and activation-regulated chemokine (TARC) is a chemokine responsible for the recruitment of Th2 cells. This study was undertaken to explore a possible role of CCL17/TARC in CSS. METHODS: CCL17/TARC levels in serum from patients with active or inactive CSS, hypereosinophilic syndrome, systemic small-vessel vasculitis other than CSS, other types of eosinophilia, and healthy controls were determined by enzyme-linked immunosorbent assay. Biopsy samples of affected tissue from CSS patients were examined by immunohistochemical staining for Th2 infiltration and CCL17/TARC expression. RESULTS: Serum CCL17/TARC levels were significantly elevated in CSS patients with active disease (mean ± SEM 1,122.0 ± 422.7 pg/ml) compared with controls (220.6 ± 27.9 pg/ml) and patients with inactive disease (388.9 ± 72.6 pg/ml) (P < 0.001 and P < 0.05, respectively). These levels correlated with the clinical disease course of CSS and with absolute eosinophil counts as well as IgE levels. Infiltrating Th2 cells in active CSS lesions were evidenced by CD294 staining. CCL17/TARC in the affected tissue of CSS patients was readily identified by immunohistochemical analysis. Elevated CCL17/TARC levels were also noted in patients with hypereosinophilic syndrome (794.5 ± 294.8 pg/ml) and other disorders associated with eosinophilia (1,096.0 ± 345.3 pg/ml) (both P < 0.005 versus controls). CONCLUSION: CCL17/TARC may contribute to CSS pathogenesis by recruitment of Th2 cells into affected tissue. Serum CCL17/TARC levels reflect disease activity, and further studies to validate its use as an activity marker in CSS are warranted.

Musculoskeletal disease burden of hereditary hemochromatosis.

OBJECTIVE: To determine the prevalence, clinical picture, and disease burden of arthritis in patients with hereditary hemochromatosis. METHODS: In this cross-sectional observational study of 199 patients with hemochromatosis and iron overload, demographic and disease-specific variables, genotype, and organ involvement were recorded. The prevalence, intensity, and localization of joint pain were assessed, and a complete rheumatologic investigation was performed. Radiographs of the hands, knees, and ankles were scored for joint space narrowing, erosions, osteophytes, and chondrocalcinosis. In addition, the number and type of joint replacement surgeries were recorded. RESULTS: Joint pain was reported by 72.4% of the patients. Their mean ± SD age at the time of the initial joint symptoms was 45.8 ± 13.2 years. If joint pain was present, it preceded the diagnosis of hemochromatosis by a mean ± SD of 9.0 ± 10.7 years. Bony enlargement was observed in 65.8% of the patients, whereas synovitis was less common (13.6%). Joint space narrowing and osteophytes as well as chondrocalcinosis of the wrist and knee joints were frequent radiographic features of hemochromatosis. Joint replacement surgery was common, with 32 patients (16.1%) undergoing total joint replacement surgery due to severe OA. The mean ± SD age of these patients was 58.3 ± 10.4 years at time of joint replacement surgery. Female sex, metacarpophalangeal joint involvement, and the presence of chondrocalcinosis were associated with a higher risk of early joint failure (i.e., the need for joint replacement surgery). CONCLUSION: Arthritis is a frequent, early, and severe symptom of hemochromatosis. Disease is not confined to involvement of the metacarpophalangeal joints and often leads to severe damage requiring the replacement of joints.

Validation of a radiographic scoring system for haemochromatosis arthropathy.

BACKGROUND: Arthropathy is one of the earliest and most common manifestations of hereditary haemochromatosis with a significant impact on quality of life. Although its radiographic features are well known, there is no assessment tool for their evaluation. OBJECTIVE: To develop and validate a novel scoring system for the evaluation of radiographic features of haemochromatosis arthropathy. METHODS: A dichotomous scoring system assessing four radiographic features of haemochromatosis arthropathy and a 4-grade scale reflecting severity of radiographic change have been developed. Standard radiographs (hand, wrist, knee and ankle) of 170 subjects (116 male, 54 female) with genetically confirmed haemochromatosis and laboratory signs of iron overload were assessed by three readers and construct validity, feasibility and cross-sectional reliability (intrareader and inter-reader) were assessed. RESULTS: Intrareader and inter-reader reliability as assessed by percentage pairwise agreement and Cohen's weighed κ were good to excellent for most features and locations evaluated. Radiographic scores correlated well with clinical parameters (bony swollen joint count, hand function and physician's global health assessment; Pearson's correlation, r²=0.18-0.62, p<0.0001). A complete set of radiographs took 3.4 ± 1.2 (mean ± SD) min to be assessed. An atlas of characteristic radiographic features was compiled. CONCLUSION: A feasible and reliable radiological assessment tool for the evaluation of haemochromatosis arthropathy has been validated and an atlas of characteristic radiographic features provided.

Analysis of gene expression in rheumatoid arthritis and related conditions offers insights into sex-bias, gene biotypes and co-expression patterns.

The era of next-generation sequencing has mounted the foundation of many gene expression studies. In rheumatoid arthritis research, this has led to the discovery of important candidate genes which offered novel insights into mechanisms and their possible roles in the cure of the disease. In the last years, data generation has outstripped data analysis and while many studies focused on specific aspects of the disease, a global picture of the disease is not yet accomplished. Here, we analyzed and compared a collection of gene expression information from healthy individuals and from patients suffering under different arthritis conditions from published studies containing the following clinical conditions: early and established rheumatoid arthritis, osteoarthritis and arthralgia. We show comprehensive overviews of this data collection and give new insights specifically on gene expression in the early stage, into sex-dependent gene expression, and we describe general differences in expression of different biotypes of genes. Many genes that are related to cytoskeleton changes (actin filament related genes) are differently expressed in early rheumatoid arthritis in comparison to healthy subjects; interestingly, eight of these genes reverse their expression ratio significantly between men and women compared early rheumatoid arthritis and healthy subjects. There are some slighter changes between men and woman between the conditions early and established rheumatoid arthritis. Another aspect are miRNAs and other gene biotypes which are not only promising candidates for diagnoses but also change their expression grossly in average at rheumatoid arthritis and arthralgia compared to the healthy condition. With a selection of intersecting genes, we were able to generate simple classification models to distinguish between healthy and rheumatoid arthritis as well as between early rheumatoid arthritis to other arthritides based on gene expression.

IRF1 is critical for the TNF-driven interferon response in rheumatoid fibroblast-like synoviocytes : JAKinibs suppress the interferon response in RA-FLSs.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by persistent synovial inflammation. The major drivers of synovial inflammation are cytokines and chemokines. Among these molecules, TNF activates fibroblast-like synoviocytes (FLSs), which leads to the production of inflammatory mediators. Here, we show that TNF regulates the expression of the transcription factor interferon regulatory factor 1 (IRF1) in human FLSs as well as in a TNF transgenic arthritis mouse model. Transcriptomic analyses of IRF1-deficient, TNF-stimulated FLSs define the interferon (IFN) pathway as a major target of IRF1. IRF1 expression is associated with the expression of IFNß, which leads to the activation of the JAK-STAT pathway. Blocking the JAK-STAT pathway with the Janus kinase inhibitor (JAKinib) baricitinib or tofacitinib reduces the expression of IFN-regulated genes (IRGs) in TNF-activated FLSs. Therefore, we conclude that TNF induces a distinct inflammatory cascade, in which IRGs are key elements, in FLSs. The IFN-signature might be a promising biomarker for the efficient and personalized use of new treatment strategies for RA, such as JAKinibs.

mTOR Senses Environmental Cues to Shape the Fibroblast-like Synoviocyte Response to Inflammation.

Accumulating evidence suggests that metabolic master regulators, including mTOR, regulate adaptive and innate immune responses. Resident mesenchymal tissue components are increasingly recognized as key effector cells in inflammation. Whether mTOR also controls the inflammatory response in fibroblasts is insufficiently studied. Here, we show that TNF signaling co-opts the mTOR pathway to shift synovial fibroblast (FLS) inflammation toward an IFN response. mTOR pathway activation is associated with decreased NF-κB-mediated gene expression (e.g., PTGS2, IL-6, and IL-8) but increased STAT1-dependent gene expression (e.g., CXCL11 and TNFSF13B). We further demonstrate how metabolic inputs, such as amino acids, impinge on TNF-mTORC1 signaling to differentially regulate pro-inflammatory signaling circuits. Our results define a critical role for mTOR in the regulation of the pro-inflammatory response in FLSs and unfold its pathogenic involvement in TNF-driven diseases, such as rheumatoid arthritis (RA).